Peroxide test strip

ABSTRACT

A composition, method, and test device for quantitatively determining the peroxide concentration of a test sample are disclosed. The test device includes a test pad having a suitable carrier matrix incorporating an indicator reagent composition capable of interacting with peroxide to produce a detectable and measurable response for peroxide over a range of 0% to over 4%, by weight of the test sample. An indicator reagent composition contains: (a) an iodide salt, (b) a buffer, and (c) a water-soluble polymer, preferably a cellulose-based polymer. An indicator reagent composition is incorporated into a carrier matrix, like filter paper, to provide a test pad useful in a dry phase peroxide assay of a test sample, especially for test samples containing a high concentration of peroxide.

FIELD OF THE INVENTION

The present invention relates to a composition, method, and test devicefor determining the peroxide concentration of a test sample. Moreparticularly, the present invention relates to a method and test devicefor assaying a liquid test sample for peroxide concentration over therange of 0% to greater than 4%, by weight, by using an improvedindicator reagent composition. The indicator reagent compositionundergoes a detectable and measurable response upon contact with a testsample containing a peroxide. Contrary to prior compositions, thepresent indicator reagent compositions have the advantage ofquantitatively measuring the high range of peroxide concentrationwithout diluting the test sample.

BACKGROUND OF THE INVENTION

The use of peroxide as a sanitizer or disinfectant for various types ofequipment, like food processing equipment and medical equipment, such asa hemodialysis unit, is common. Because the amount of peroxide in anaqueous solution relates directly to the disinfecting or sanitizingactivity thereof, a test which rapidly and accurately measures peroxideconcentration is important.

The use of a peroxide, like hydrogen peroxide or peracetic acid, as adisinfectant for medical equipment is widespread because of its lowcost, convenience, and effectiveness as an antiseptic agent inrelatively low concentrations. For example, peroxides are used as adisinfectant in a substantial number of hemodialysis centers. Peroxidesare used in hemodialysis centers to sanitize hemodialysis units becauseperoxides are an effective and economical sanitizing agent. It also isimportant to clean and disinfect a hemodialysis unit between eachdialysis session to prevent pathogen contamination from patient topatient.

When a sanitizing solution is used in medical or food processingequipment, two critical peroxide levels must be monitored. First, theperoxide concentration must be sufficiently high to perform a sanitizingor disinfecting function, i.e., at least about 500 ppm (parts permillion) peroxide is needed to effectively sanitize equipment. Duringthe sanitizing process, the sanitizing solution is assayed periodicallyto ensure that sufficient peroxide is present to sanitize the equipment.

After the sanitizing function is completed, and before reuse, theequipment is rinsed with water to flush residual peroxide from theequipment. The rinse water also is assayed for peroxide to ensure thatthe level of residual peroxide is below the maximum allowable level.

Presently, there is one type of commercial assay system for assayinghemodialysis units for peroxide concentration. The assay issemiquantitative and merely indicates that sufficient peroxide ispresent to sanitize the equipment, or that the peroxide is below thissanitizing level. No other quantitative information is available fromthe assay. This assay relies on a color transition formed by a starchiodine complex.

A starch-iodide solution had been used as an indicator foroxidation-reduction (redox) titrations for decades. The starch iodinecomplex has a sharp and intense color transition, turning from colorlessfor the iodide ion to dark blue for the starch iodine complex. A starchiodine color transition, therefore, is used mainly as an end pointindicator. The color intensity of the starch iodine complex formation isso great that the color transition from iodide to iodine does not allowa quantitative distinction between different concentrations of anoxidant, like peroxide, present in a test sample. Consequently, therewas little to no impetus to use formation of a starch iodine complex ina quantitative calorimetric determination of an oxidant in a testsample, especially at high oxidant concentrations.

To be useful in a quantitative assay, color transitions must bedifferentiable and related to the concentration of the analyte ofinterest. Therefore, it is necessary to find a color-forming complexthat undergoes a color transition of weaker intensity than the starchiodine complex. The identity of this less intensely colored complex hasevaded workers in the art, especially with respect to an assay for aperoxide in a high concentration range of about 0.1% to greater thanabout 4% by weight of the test sample.

The search for a compound that binds to iodine, and forms a coloredcomplex suitable for use in a quantitative assay for an oxidant, likeperoxide, has not been successful until the present disclosure. Forexample, M. M. Zwick, Journal of Applied Polymer Science, Vol. 9, pp.2393-2424 (1965), discloses formation of blue color complex of iodineand polyvinylalcohol. The Zwick publication discloses a structuralrequirement and mechanism for the formation of an iodine-polymercomplex, but does not address or consider a relationship between colorintensity of the complex and iodine concentration. Furthermore, theZwick publication fails to suggest any utility of a colorediodine-polymer complex, in particular in an assay for peroxideconcentration in aqueous solution.

Various patents are directed to the starch iodine complex as theindicator in an assay of a test sample. U.S. Pat. Nos. 3,814,668 and4,303,753 disclose the use of potassium iodide as a redox indicator inthe presence of polyvinylpyrrolidone (PVP) for detection of glucose inurine. Such an indicator system is used in the DIASTIX® urine glucosetest strip, marketed by Bayer Diagnostics, Elkhart, Ind. The maximumcolor intensity for glucose concentration is 2000 mg/dL, which isstoichiometrically equivalent to 111 mM hydrogen peroxide, and which, inturn, is equivalent to 3777 mg/L or 0.37% by weight of hydrogenperoxide. Because only a fraction of glucose in the test sample isactually reacted to release hydrogen peroxide, the indication isresponding to an actual peroxide concentration that is probably muchless than the calculated level of 0.37% by weight.

Similarly, U.S. Pat. No. 4,621,049 discloses the use of iodide ion andPVP as an indicator in an assay for measuring a glucose concentration ashigh as 10,000 mg/dL. In such a assay, however, the ability to measure ahigh range of glucose is achieved by modulating enzyme reactivitythrough a borate buffer at an alkaline pH, as disclosed in the U.S. Pat.No. 5,217,691. The indicator system, again, is responding to only afraction of glucose in the test sample. Therefore, the indicator used inDIASTIX® is responding only to low levels of hydrogen peroxide, and doesnot disclose or suggest an ability to respond to a peroxideconcentration of 0.1%, by weight, or higher. Other patents directed toiodide/iodine indicators are U.S. Pat. Nos. 4,181,500 and 4,992,296.

To date, no known single assay is available to assay a wide peroxideconcentration range because the large peroxide concentration differencemakes detection and differentiation between concentration levelsdifficult. The present invention is directed to providing an assay forperoxide that is capable of measuring peroxide concentration over therange of 0% to about 4%, and especially about 0.1% to about 4%, byweight, without diluting the test sample.

The present invention, therefore, is directed to an assay method anddevice that can be used to test sample containing 0% to 4% or more ofperoxide, without diluting the solution. As illustrated hereafter, thepresent test strips have a good sensitivity and a wide detection rangewith a continuous color response from 0.1% to over 4%, by weight,peroxide, without diluting the test sample.

The present method of assaying for peroxide in an aqueous test sampleyields trustworthy and reproducible results by utilizing an indicatorreagent composition that undergoes a color transition in response toperoxide concentration, and not as a result of a competing chemical orphysical interaction, such as a preferential interaction with anothertest sample component. Additionally, the method and composition utilizedin the peroxide assay does not adversely affect or interfere with anyother test reagent pads that are present on a multiple test pad strip.

In accordance with the present invention, an indicator reagentcomposition can be incorporated into a carrier matrix to providesufficient sensitivity and color differentiation to assay for peroxideconcentration over the range of 0% to greater than about 4%, andparticularly about 0.1% to greater than about 4%, by weight, withoutsample dilution. In addition, although dry phase test strips have beenused to assay for peroxide concentration, no dry phase test strip hasbeen used to quantitatively assay an undiluted test sample for peroxideat the high concentration range.

SUMMARY OF THE INVENTION

In brief, the present invention is directed to a new and improvedcomposition, test device, and method of determining the peroxideconcentration of a test sample. A device includes a test pad comprisinga suitable carrier matrix incorporating an indicator reagent compositioncapable of interacting with a peroxide to produce a detectable responseto peroxide concentration. A carrier matrix of the test pad comprises abibulous material, such as filter paper; a nonbibulous material, such asa strip, layer, or membrane of a polymerized material; or a mixturethereof. An indicator reagent composition is homogeneously incorporatedinto the carrier matrix, and the carrier matrix then holds the indicatorreagent composition homogeneously throughout the carrier matrix whilemaintaining carrier matrix penetrability by the test sample.

More particularly, the present invention is directed to a method ofassaying for the peroxide content of aqueous test samples by utilizing anew indicator reagent composition. It has been demonstrated that areagent composition including: (a) an iodide salt, (b) a buffer, like apolycarboxylic acid, and (c) a water-soluble polymer, and preferably acellulose-based polymer, affords sufficient sensitivity to test sampleperoxide content, and a sufficient color differentiation between testsamples having a different peroxide content over the range of 0% togreater than about 4%, and particularly about 0.1% to greater than about4%, by weight.

In accordance with an important feature of the present invention, anaccurate and reliable quantitative determination for peroxide in anundiluted test sample is achieved because the indicator reagentcomposition undergoes a differentiable color transition in response tothe peroxide content of the test sample, even at a high concentration ofperoxide. By utilizing an indicator reagent composition of the presentinvention, the quantitative assay for peroxide in liquid test samples ismore sensitive and accurate because the indicator reagent composition isable to detect, and differentiate between, high levels of peroxidepresent in a test sample.

Therefore, one aspect of the present invention is to provide a methodand composition for quantitatively determining the peroxideconcentration of an aqueous liquid. The composition interacts with theperoxide to produce a change in color of a test device that isindicative of the peroxide concentration of the test sample.

Another aspect of the present invention is to provide a method ofassaying aqueous test samples, said method having sufficient sensitivityand sufficient visual color resolution to allow differentiation between,and the quantitative measurement of, test samples having differentperoxide concentrations.

Yet another object of the present invention is to provide a sensitivemethod of assaying undiluted test samples for peroxide concentrationover the range of 0% to greater than about 4% by weight peroxide. Thepresent method is especially useful in the detection of a highconcentration of peroxide, i.e., about 0.1% to greater than about 4%, byweight of the test sample.

Another aspect of the present invention is to provide an indicatorreagent composition that interacts with peroxide and undergoes avisually or instrumentally differentiable color transition to allow thedetermination of peroxide concentration of a test sample.

Another aspect of the present invention is to provide a method ofassaying for the peroxide content of a liquid test sample byincorporating an indicator reagent composition into a dry phasedetection device, wherein the indicator reagent composition comprises:(a) an iodide salt, (b) a buffer, (c) a water-soluble polymer,preferably a cellulose-based polymer, and (d) a suitable carrier.

Still another aspect of the present invention is to provide a new andimproved method of assaying for the peroxide content of an aqueous testsample by utilizing a test device, including a carrier matrix, saidcarrier matrix comprising a bibulous matrix, like filter paper, or anonbibulous matrix, like a glass fiber or a layer of a permeablepolymeric material, and said carrier matrix having incorporated thereinan indicator reagent composition capable of interacting with peroxidepresent in the test sample, to provide a color transition that can becorrelated to the peroxide concentration of the test sample.

A further aspect of the present invention is to provide an improved dryphase test strip that incorporates an indicator reagent compositioncomprising an iodide salt, a buffer, and a water-soluble polymer, intothe carrier matrix, and thereby provide a quantitative assay for theperoxide content of a test sample.

The above and other aspects and advantages and novel features of thepresent invention will become apparent from the following detaileddescription of the preferred embodiments.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

In accordance with the method of the present invention, a quantitativeassay of aqueous test samples for peroxide content, and especially highconcentrations of a peroxide, is accomplished by utilizing an indicatorreagent composition that includes (a) an iodide salt, (b) a buffer, and(c) a water-soluble polymer, preferably a cellulose-based polymer. Byemploying an indicator reagent composition of the present invention,sufficient sensitivity and sufficient visual color differentiationbetween test samples of different peroxide content is achieved. Inaccordance with the method of the present invention, undiluted testsamples having a peroxide content of 0% to greater than about 4%, andparticularly about 0.1% to greater than about 4%, by weight of the testsample, can be measured and differentiated.

To achieve the full advantage of the present invention, the method andcomposition are employed in dry phase, test pad assays to determine theperoxide concentration of aqueous test samples. A dry phase test strip,including a test pad comprising a carrier matrix incorporating anindicator reagent composition of the present invention, allows the rapidquantitative assay of undiluted test samples by visual means.

In particular, the present invention allows determination of theperoxide concentration of a test sample by the visual color change of atest pad on a test strip resulting from contact between the test stripand the test sample. Peroxide concentration of the test sample isdetermined by correlating the detected color change to the peroxideconcentration of the test sample. The test strip includes a test padcomprising an inert carrier matrix incorporating an indicator reagentcomposition. The present composition and method allow the rapidcolorimetric determination of the peroxide concentration of a testsample, and especially high peroxide concentrations.

Previous assay methods employed compositions that were unable todistinguish between aqueous solutions containing differentconcentrations of peroxide above about 0.1%, by weight. The priorcompositions utilized starch as a polymer, which forms a complex withiodine having a high color intensity, thereby making differentiationbetween color transitions, and peroxide concentration, difficult toimpossible. In contrast, the present method measures peroxide content byutilizing an indicator reagent composition containing a water-solublepolymer that forms a complex with iodine having a weaker color intensitythan a starch iodine complex, such that color transitions resulting fromdifferent peroxide concentrations can be differentiated and quantified.

One component of the present indicator reagent composition is the iodineindicator. The peroxide in the test sample reacts with iodide ion toform iodine. The iodine then is available to complex with awater-soluble polymer that also is present in the indicator reagentcomposition.

Therefore, the indicator reagent composition contains an iodide salt,and typically potassium iodide. However, any water-soluble iodide salthaving a cation that does not interfere with the assay for peroxide canbe used. Examples of other iodide salts are sodium iodide and lithiumiodide.

In accordance with an important feature of the present invention, theiodine-polymer complex undergoes a color transition through variousdetectable and measurable degrees and intensities of color such that thedegree and intensity of the color transition can be correlated to theconcentration of peroxide in a test sample. In accordance with anotherimportant feature of the present invention, the indicator reagentcomposition undergoes a differentiable color transition at high peroxideconcentrations, and, therefore, it is unnecessary to dilute the testsample. The ability to assay an undiluted test sample eliminates acommon source of error from the assay.

The iodide salt typically is present in the indicator reagentcomposition in an amount of about 1% to about 4%, and preferably in anamount of about 1.5% to about 3%, by weight of the indicator reagentcomposition. To achieve the full advantage of the present invention, theiodide ion is present in an amount of about 1.75% to about 2.75%, byweight of the indicator reagent composition. In general, however, theamount of iodide salt included in the indicator reagent composition islimited only in that the composition undergoes a detectable colortransition in proportion to the concentration of peroxide in a testsample.

In accordance with an important feature of the present invention, it wasfound that iodine can bind to polymers other than starch to form acomplex that is weaker than a starch iodine complex, and accordinglygenerates a weaker color transition. Such iodine-polymer complexes ofthe present invention can be used to detect and quantify the amount ofperoxide in a test sample.

It was found that iodine can bind with water-soluble polymers, andespecially cellulose-based polymers, to form a color complex having areddish-brown color. The color intensity and hue is related to theidentity of the water-soluble polymer present in the iodine-polymercomplex. Therefore, by proper selection of a water-soluble polymer, ormixture of polymers, it is possible to generate a scale ofdifferentiable colors that correlate to a specific concentration rangeof peroxide.

In searching for a polymer that forms a weak iodine/polymer complex, andhaving weaker color intensity than an iodine-starch complex, it wassurprising to find that iodine complexes with water-soluble polymers,such as hydroxypropylcellulose, to form a reddish-brown color. In thepresence of an excess amount of polymer, iodine, which is formed byoxidation of iodide ion by an oxidant, like peroxide, forms variousdegrees of reddish-brown color corresponding to the concentration of theoxidant in a test sample. The color transitions then can be used toquantify the concentration of oxidant in the test sample by correlatingthe color transition to known concentrations of oxidant.

Therefore, in addition to an iodide salt, the indicator reagentcomposition contains a water-soluble polymer. The water-soluble polymeris a nonionic or anionic polymer, and preferably is a cellulose-basedpolymer. However, other water-soluble polymers, such aspolyvinylpyrrolidone, also can be used as the polymer in a presentindicator reagent composition. In preferred embodiments, the indicatorreagent composition contains a mixture of cellulose-based polymers. Inespecially preferred embodiments, the indicator reagent compositioncontains a mixture of cellulose-based polymers, and an additionalwater-soluble polymer.

The water-soluble polymer is present in the indicator reagentcomposition in an amount of about 0.1% to about 5%, and preferably about0.2% to about 3%, by weight of the indicator reagent composition. Toachieve the full advantage of the present invention, the water-solublepolymer is present in the indicator reagent composition in an amount ofabout 0.5% to about 2.5%, by weight of the composition.

The preferred water-soluble polymers are cellulose-based polymers. Inmost preferred embodiments, the indicator reagent composition contains amixture of water-soluble polymers to achieve a broad range quantitativeassay, and particularly a high range quantitative assay, for peroxide. Amixture of water-soluble polymers also can provide an indicator reagentcomposition that responds to a specific peroxide concentration range.

The water-soluble, cellulose-based polymers are derivatives of cellulosewherein hydroxy groups on the sugar moiety of cellulose are modifiedwith a short chain alkyl (i.e., C₁ -C₄), alkyl alcohol, or alkylcarboxylic acid. Examples of some common cellulose modifications arereplacing a portion of the hydroxy groups with methyl, hydroxymethyl,hydroxyethyl, hydroxyethylmethyl, hydroxypropyl, hydroxypropylmethyl, orcarboxymethyl groups, for example.

The color intensity of an iodine-polymer complex is inverselyproportional to the number of carbon atoms in the modifying moiety. Forexample, a cellulose-based polymer having hydroxyethyl groups forms adarker brown color than a cellulose-based polymer having a hydroxypropylgroup. Accordingly, color intensity is related to the hydrophilicity ofthe polymer. For example, hydroxyethylcellulose is soluble only inwater, but not in organic solvents, whereas hydroxypropylcellulose issoluble in both water or organic solvent. Carboxymethylcellulose ishighly soluble in water, and forms dark brown color with iodine.

Examples of water-soluble cellulose-based polymers useful in the presentinvention include, but are not limited to, methylcellulose,hydroxymethylcellulose, hydroxyethylcellulose,hydroxyethylmethylcellulose, hydroxypropylcellulose,hydroxypropylmethylcellulose, carboxymethylcellulose and salts thereof,hydroxybutylcellulose, cellulose acetate,carboxymethylhydroxyethylcellulose, hydroxybutylmethylcellulose, andmixtures thereof. As illustrated hereafter, a blend of two or morewater-soluble cellulose-based polymers provides a more intense colortransition in response to peroxide and gives a wider color response toperoxide concentrations.

In addition to cellulose-based polymers, other water-soluble polymerscan be used in the method and composition of the present invention. Suchwater-soluble polymers are nonionic or anionic in character. Examples ofuseful water-soluble polymers include, but are not limited to,polyvinylpyrrolidone, hydrolyzed polyvinylpyrrolidone, poly(vinylalcohol), poly(vinyl acetate), vinyl acetate-vinyl alcohol copolymers,polyvinyloxazolidone, polyvinylmethyloxazolidone, copolymers ofvinylpyrrolidone and a vinyl amide of γ-amine butyric acid, polyacrylicacid polymers, polyacrylic acid copolymers, partially or fullyneutralized salts of polyacrylic acid polymers and polyacrylic acidcopolymers, poly(methacrylic acid), poly(methacrylamide),poly(N,N-dimethylacrylamide), poly(N-isopropylacrylamide),poly(N-acetamidoacrylamide), poly(N-acetamidomethacrylamide), acrylicinterpolymers of polyacrylic acid with poly(methacrylic acid),polyacrylic acid with poly(methacrylamide), polyacrylic acid withmethacrylic acid, polyoxypropylene-polyoxyethylene block polymers havingone of the following structures: ##STR1## wherein x and z,independently, are an integer from about 4 to about 30, and y is aninteger from about 4 to about 100, polyacrylamide, copolymers ofacrylamide, acrylamide/sodium acrylate copolymers, acrylate/acrylamidecopolymers, acrylate/ammonium methacrylate copolymers,acrylate/diacetoneacrylamide copolymers, acrylic/acrylate copolymers,adipic acid/dimethylaminohydroxypropyl diethylenetriamine copolymers,ammonium acrylate copolymers, ammonium styrene/acrylate copolymers,ammonium vinyl acetate/acrylate copolymers, aminomethylpropanolacrylate/diacetoneacrylamide copolymers, aminomethylpropanediolacrylate/diacetoneacrylamide copolymers, butyl benzoic acid/phthalicanhydride/trimethylolethane copolymers, diethyleneglycolamine/epichlorohydrin/piperazine copolymers, ethylene/vinylalcohol copolymers, ethyl esters of polyethylenimines, isopropyl esterof methyl vinyl ether/maleic anhydride copolymers, melamine/formaldehyderesin, methoxyethylene glycol/dodecyl glycol copolymers,octadecene/maleic anhydride copolymers,octylacrylamide/acrylate/butylaminoethyl methacrylate copolymers,octylacrylamide/acrylate copolymers, polyethylene glycol/dodecyl glycolcopolymers, polyethyleneimine, phthalic anhydride/glycerin/glycidyldecanoate copolymers, metal salts of polyacrylic acid, metal salts ofmethyl vinyl ether/maleic anhydride copolymers,vinylpyrrolidone/eicosene copolymers, vinylpyrrolidone/ethylmethacrylate/methacrylic acid copolymers, vinylpyrrolidone/hexadecenecopolymers, vinylpyrrolidone/vinyl acetate copolymers,polyvinylpyrrolidone/vinyl acetate/itaconic acid copolymers, sodiumacrylate/vinyl alcohol copolymers, sodium polymethacrylate, sodiumpolystyrene sulfonate, sodium styrene/acrylate/polyethylene glycol-10dimaleate copolymers, sodium styrene/polyethylene glycol-10maleate/nonoxynol-10 maleate/acrylate copolymers, styrene/acrylamidecopolymers, styrene/acrylate/ammonium methacrylate copolymers,styrene/maleic anhydride copolymers, styrene/polyvinyloxazolidonecopolymers, urea formaldehyde polymers, urea/melamine/formaldehydepolymers, vinyl acetate/crotonic acid copolymers, vinyl alcoholcopolymers, and mixtures thereof.

In addition to the iodide salt and water-soluble polymer, the indicatorreagent composition also contains a buffer. In accordance with animportant feature of the present invention, the buffer buffers theindicator reagent composition at a pH of about 2 to about 9, andpreferably about 4 to about 7. To achieve the full advantage of thepresent invention, the buffer buffers the indicator reagent compositionat a pH of about 5 to about 6.5.

The identity of the buffer is not particularly limited, as long as theindicator reagent composition is buffered at a pH of about 2 to about 9.Therefore, useful buffers include, but are not limited to,polycarboxylic acids, phosphate, borate, acetate, and mixtures thereof.Preferred buffers are polycarboxylic acids, and especiallypolycarboxylic acids wherein the carboxyl groups are separated by two tofive carbon atoms. Examples of useful polycarboxylic acid buffersinclude, but are not limited to, citric acid, succinic acid, lacticacid, and ketoglutaric acid. The concentration of buffer in thecomposition typically is about 1% to about 15%, and preferably about 5%to about 12%, by weight, of the composition.

In addition to the iodide salt, the water-soluble polymer, and thebuffer, the indicator reagent composition also can contain optionalingredients. For example, one optional ingredient is a surfactant, inparticular an anionic surfactant or a nonionic surfactant. Thesurfactant improves the ability of the test sample to wet the carriermatrix, and the surfactant also improves the stability of the colortransition of the indicator in response to peroxide.

The surfactant is present in the indicator reagent composition in anamount of 0% to about 1.5%, and preferably about 0% to about 1%, byweight of the composition. To achieve the full advantage of the presentinvention, the surfactant is present in an amount of about 0% to about0.5% by weight of the composition.

Useful nonionic surfactants include, but are not limited to, anethoxylated polysorbate, e.g., polysorbate 20 through polysorbate 85, anethoxylated alcohol, e.g., a C₁₀ to C₂₂ alcohol ethoxylated with about10 to about 25 moles of ethylene oxide, an ethoxylated phenol, i.e., anethoxylated octylphenol, nonylphenol, or dodecylphenol with about 8 toabout 30 moles of ethylene oxide, a polyethylene glycol, e.g., PEG-8through PEG-40, a polypropylene glycol, e.g., PPG-9 through PPG-34, anethylene glycol-propylene glycol copolymer, e.g., a poloxamer, apolybutylene glycol, and similar nonionic surfactants, and mixturesthereof. In general, a useful nonionic surfactant has an HLB value ofabout 6 to about 25.

Anionic surfactants useful in the present invention are not particularlylimited. Usually, the anionic surfactant includes a hydrophobic moiety,such as a carbon chain including about eight carbon atoms to about 30carbon atoms, and particularly about twelve carbon atoms to about twentycarbon atoms; and further includes a hydrophilic moiety, such assulfate, sulfonate, carbonate, phosphate, or carboxylate. Often, thehydrophobic carbon chain is etherified, such as with ethylene oxide orpropylene oxide, to impart a particular physical property or reducedsurface tension, to the anionic surfactant.

The anionic surfactants are well known, and can be a fatty acid, a saltof a fatty acid, an ethoxylated fatty acid, or a salt of an ethoxylatedfatty acid, for example. Therefore, suitable anionic surfactantsinclude, but are not limited to, compounds in the classes known as alkylsulfates, alkyl ether sulfates, alkyl ether sulfonates, sulfate estersof an alkylphenoxy polyoxyethylene ethanol, alpha-olefin sulfonates,beta-alkyloxy alkane sulfonates, alkyl arylsulfonates, alkyl carbonates,alkyl ether carboxylates, fatty acids, sulfosuccinates, alkyl ethersulfosuccinates, sarcosinates, octoxynol phosphates, nonoxynolphosphates, taurates, fatty taurides, sulfated monoglycerides, fattyacid amido polyoxyethylene sulfates, and isothienates; or mixturesthereof. Many additional anionic surfactants are described inMcCutcheon's, Detergents and Emulsifiers, 1993 Annual, published byMcCutcheon Division, M. C. Publishing Co., and incorporated herein byreference.

Usually, the anionic surfactant is present in the composition as aneutralized salt in the form of a sodium, potassium, lithium, ammonium,alkylammonium, or hydroxyalkylammonium salt, wherein the alkyl moietyincludes one to about three carbon atoms. The alkyl sulfates and alkylether sulfates are particularly effective classes of anionicsurfactants. Consequently, examples of anionic surfactants useful in thecomposition and method of the present invention include, but are notlimited to, the ammonium, monoethanolamine, diethanolamine,triethanolamine, isopropylamine, sodium, potassium, lithium, ormagnesium salt of lauryl sulfate, dodecylbenzenesulfonate, laurylsulfosuccinate, lauryl ether sulfate, lauryl ether carboxylate, laurylsarcosinate, cocomethyl tauride, and sulfosuccinate half ester amide; ormixtures thereof. Examples of especially useful anionic surfactants area lauryl sulfate salt, a lauryl ether sulfate salt, a lauryl phosphate,a sulfosuccinate salt, a dodecylsulfonate salt, a cholate salt, a C₈ toC₁₈ fatty acid, and mixtures thereof.

A test strip of the present invention can be used to assay an undilutedtest sample for peroxide concentration. Hydrogen peroxide is a commonlyused disinfectant for hemodialysis units, but most indicator reagentcompositions cannot assay undiluted test samples for a highconcentration of peroxide because the deep color transitions cannot bedifferentiated and quantified.

In contrast, a present test strip can be used to assay undiluted testsamples for peroxide over the range of 0% to greater than about 4%, andespecially about 0.1% to greater than about 4%, by weight, of thecomposition. This capability greatly increases versatility of thepresent test strips because medical workers often use hydrogen peroxideto sanitize hemodialysis units. The present test strips, therefore, canbe used by medical personnel as a test strip to assay for amounts ofsanitizing compound in the working solution.

The carrier for the ingredients of an indicator reagent compositionincludes water. However, organic solvents, such as acetone, methanol,ethanol, isopropyl alcohol, ethylene glycol, propylene glycol,dimethylformamide, dimethylsulfoxide, acetonitrile, ethyl acetate, andsimilar solvents, can be included in the carrier vehicle. The selectionof a suitable organic solvent or solvents, in addition to water, toinclude in the carrier of the indicator reagent composition is withinthe capability of those skilled in the art of designing diagnosticassays.

The amount of organic solvent present in an indicator reagentcomposition generally is 0% to about 90%, and preferably about 10% toabout 70%, by weight of the carrier. A carrier comprising water and anorganic solvent, like methanol, ethanol, or acetone, is especiallypreferred because a carrier matrix impregnated with the indicatorreagent composition can be dried within a few to several minutes.

As previously described, an indicator reagent composition undergoes acolor transition upon contact with a test sample to provide an assay forperoxide concentration from the intensity and degree of the colortransition. In accordance with an important feature of the presentinvention, an indicator reagent composition of the present inventionprovides a sufficiently resolved and differentiated color transitionsuch that the peroxide in a test sample can be measured and accuratelydetermined without the use of color-measuring instruments, such asspectrophotometers or colorimeters, over a concentration range of 0% togreater than about 4%, by weight of the composition. However, ifdesired, such color-measuring instruments can be used to measure thedifference in color degree and intensity between the test sample and asolution having a known concentration of peroxide.

The intensity and degree of the color transition are used to determinethe peroxide content of the test sample by comparing or correlating thecolor produced by the test sample to colors produced by solutions havinga known peroxide concentration. In accordance with an important featureof the present invention, the indicator reagent composition provides asufficiently resolved and differentiated color transition such that theperoxide content of an undiluted test sample can be measured for testsamples having a peroxide content of 0% to greater than about 4% byweight without the use of color-measuring instruments.

An indicator reagent composition of the present invention, as describedabove, is used in dry phase, test pad assays for peroxide. The dryphase, test pad assay for peroxide utilizing a present indicator reagentcomposition is performed in accordance with methods well known in theart. In general, the assay for peroxide is performed by contacting thetest sample with an analyte detection device that includes an indicatorreagent composition. The analyte detection device can be dipped into thetest sample, or the test sample can be applied to the analyte detectiondevice dropwise. The resulting change in color of the analyte detectiondevice reveals the peroxide concentration of the test sample; and, if sodesigned, the resulting color transition can be compared to astandardized color chart to provide a measurement of the peroxideconcentration of the test sample.

Typically, the analyte detection device is a test strip impregnated withan indicator reagent composition, designed either as a single pad teststrip (to assay only for a single analyte) or as a multiple pad teststrip (to assay for several analytes simultaneously). For either type oftest strip, the test strip includes a support strip, or handle, normallyconstructed from a hydrophobic plastic, and a reagent test pad,comprising a bibulous or nonbibulous carrier matrix. In general, thecarrier matrix is an absorbent material that allows the test sample tomove in response to capillary forces through the matrix to contact theindicator reagent composition and produce a detectable and measurablecolor transition.

The carrier matrix can be any substance capable of incorporating thechemical reagents required to perform the assay of interest, as long asthe carrier matrix is substantially inert with respect to the chemicalreagents. The carrier matrix also is porous or absorbent relative to theliquid test sample.

The expression "carrier matrix" refers either to bibulous or nonbibulousmatrices that are insoluble in the carrier of the indicator reagentcomposition and other physiological fluids and that maintain theirstructural integrity when exposed to the carrier and other physiologicalfluids. Suitable bibulous matrices include filter paper, spongematerials, cellulose, wood, woven and nonwoven fabrics, and the like.Nonbibulous matrices include glass fiber, polymeric films, andmicroporous membranes. Other suitable carrier matrices includehydrophilic inorganic powders, such as silica gel, alumina, diatomaceousearth and the like; argillaceous substances; cloth; hydrophilic naturalpolymeric materials, particularly cellulosic material, like cellulosebeads, and especially fiber-containing papers such as filter paper orchromatographic paper; synthetic or modified naturally occurringpolymers, such as cellulose acetate, polyvinyl chloride, polyacrylamide,polyacrylathanes, polyurethanes, crosslinked dextran, agarose, and othersuch crosslinked and noncrosslinked water-insoluble hydrophilicpolymers. The carrier matrix can be of different chemical compositionsor a mixture of chemical compositions. The matrix also can vary inregards to smoothness and roughness combined with hardness and softness.The handle usually is formed from hydrophobic materials such ascellulose acetate, polyethylene terephthalate, polycarbonate, orpolystyrene. The carrier matrix is most advantageously constructed fromfilter paper or polymeric films.

The carrier matrix of the test strip can be any bibulous or nonbibulousmaterial that allows permeation by the test sample to saturate the testpad of the test strip that is impregnated with the indicator reagentcomposition. A preferred carrier matrix is a hydrophilic, bibulousmatrix, including cellulosic materials, such as paper, and preferablyfilter paper. The carrier matrix also can be a hydrophilic, nonbibulousmatrix, including polymeric films, such as a polyurethane or acrosslinked gelatin. Such polymeric films possess all of the qualitiesrequired of a carrier matrix of the present invention, includingsuspending and positioning both the essential ingredients and anyoptional ingredients included in the indicator reagent composition, andpermeability of the test sample through the carrier matrix.

In accordance with the method of the present invention, to perform a dryphase test strip assay for peroxide, an aqueous solution, including: (a)about 1% to about 4%, by weight, of an iodide salt; (b) about 0.1% toabout 5% by weight of water-soluble polymer, like a cellulose-basedpolymer; (c) about 1% to about 15% by weight of a buffer; and (d) anyother desired optional ingredients, or solvents, first is prepared. Anonbibulous matrix, such as a polyurethane film, or a bibulous matrix,such as filter paper, then is saturated or impregnated with the aqueoussolution by immersing or by spraying the aqueous solution onto sheets orprecut strips or pads of the polyurethane film or filter paper.

Then, after removing the aqueous solvent by drying in a forced air ovenat a temperature of about 40° C. to about 100° C. for about 2 to about15 minutes, the impregnated polyurethane film or filter paper, ifnecessary, is cut to an appropriate size, such as a pad havingdimensions from about 0.2 in. (inch) (0.5 cm) by about 0.5 in (1.3 cm)to about 0.5 in. (1.3 cm) by about 1 in. (2.5 cm).

It should be understood that it is well within the experimentaltechniques of those skilled in the art of preparing test devices todetermine the proper balance between size of the test pad, the strengthof indicator reagent composition solutions, the amount of test sample,and the method of introducing the test sample to the test strip, such asby pipetting rather than dipping, in order to design a quantitativeassay for peroxide utilizing the method and composition of the presentinvention.

The dried, impregnated polyurethane film or filter paper then is securedto an opaque or transparent hydrophobic plastic handle with double-sidedadhesive tape. The resulting test strip then is contacted with a testsample for a sufficient time to saturate the test pad with the sample.After waiting a predetermined time, such as from about 1 to about 120seconds, the test strip is examined, either visually or by instrument,for a response. The color transition, if any, of the test pad revealsthe concentration of peroxide in the test sample.

In many cases, simple visual observation of the test strip provides thedesired information. If more accurate information is required, a colorchart bearing color spots corresponding to various known concentrationsof peroxide can be prepared for the particular indicator reagentcomposition used in the test strip. The resulting color of the teststrip after contact with the test sample then can be compared with thecolor spots on the chart to determine the concentration of peroxide inthe test sample. If a more accurate determination is required, aspectrophotometer or calorimeter can be used to more precisely determinethe degree of the color transition. In addition, the dry phase teststrip assay can be made quantitative by employing spectrophotometric orcolorimetric techniques, as opposed to visual techniques, in order tomore reliably and more accurately measure the degree of colortransition, and, therefore, more accurately measure the concentration ofperoxide in the test sample.

In accordance with one embodiment of the present invention, thefollowing dry phase test strips were prepared to perform a dry phaseassay for peroxide. A strip, a pad, or a sheet of a carrier matrix, likefilter paper, such as Whatman 54, available from Whatman Ltd.,Maidstone, Kent, U. K., or S&S 404, first was immersed into an aqueoussolution containing:

    ______________________________________    INDICATOR REAGENT COMPOSITION    Ingredient             Amount    ______________________________________    Water                  18 g (grams)    Citrate Buffer 1M (pH 5.5)                           2 g    Water-soluble Polymer  0.2 g    Potassium Iodide       0.5 g    ______________________________________

Excess solution was removed from the surface of the filter paper with ascraper bar.

The impregnated filter paper then was dried in a forced air oven havinga temperature of about 60° C. to about 80° C. for about 10 minutes. Thedried impregnated filter paper then was backed with a double-sidedadhesive, and slit into 0.2 inch (0.5 cm) wide ribbons. A ribbon offilter paper incorporating an indicator reagent composition of thepresent invention then was attached to a polystyrene plastic support bymeans of the double-sided adhesive. The plastic support, including thesaturated or impregnated filter paper, then was slit into 0.2 inch (0.5cm) wide strips. Accordingly, the plastic support included a pad havingdimensions of about 0.2 inch (0.5 cm) by about 0.2 inch (0.5 cm) ofsaturated or impregnated filter paper to provide a test pad comprising afilter paper carrier matrix incorporating an indicator reagentcomposition of the present invention.

To demonstrate the new and unexpected results achieved by the method ofthe present invention, dry phase test strips incorporating an indicatorreagent composition of the present invention were used to assaystandardized solutions containing hydrogen peroxide or peracetic acid.Individual test strips, containing different water-soluble polymers,were prepared from the indicator reagent composition described above.Individual strips were dipped into a series of standardized solutions,containing from 0.5% to 3% by weight hydrogen peroxide, or 100 to 2000ppm peracetic acid.

The test strips also can be used to assay for other peroxides andperacids, such as benzoyl peroxide, performic acid, perbenzoic acid,alkyl and cycloalkyl hydroperoxides having the formula R--OOH, wherein Ris an alkyl or cycloalkyl group having one to ten carbon atoms andoptionally substituted with a phenyl group, peroxypropanoic acid,peroxybutyric acid, and other peracids having the formula R₁ --CO₃ H,wherein R₁ is hydrogen, an alkyl or cycloalkyl group containing 1 to 15carbon atoms, or phenyl.

The standardized solutions were assayed for peroxide by contacting atest strip with a standardized solution for about one (1) second. Thecolor of the test strips then was observed. Timing of the strip reactionis not critical. However, for consistency, the strip color was evaluatedafter 30 seconds in each test. The test results set forth in Tables 1and 2 illustrate the difference in color transition provided bydifferent iodide/polymer mixtures to an increasing peroxideconcentration. Tables 1 and 2 also show that an iodide/starch mixtureprovided too intense of a color transition, and, accordingly,quantitative differences in peroxide concentration could not bedetermined. In each test, the test strip was colorless prior toimmersion into a standardized test sample.

                  TABLE 1    ______________________________________    Color response of iodine-polymer complex to increasing    hydrogen peroxide concentration               Hydrogen Peroxide Concentration    Polymer      0.5%     1.0%     2.0%   3.0%    ______________________________________    Hydroxypropylcellulose                 Yellow   Lt Brown Brown  Brick    Hydroxyethylcellulose                 Lt Brown Brown    Brick  Dk Coffee    Carboxymethylcellulose                 Brown    Dk Brown Dk Coffee                                          Dk Coffee    Polyvinylpyrrolidone                 Y Brown  Brick    Brick  Brick    (PVP)    Starch       Bk Blue  Bk Blue  Bk Blue                                          Bk Blue    ______________________________________     Abbreviations: Y = yellow, Lt = light, Dk = Dark, Bk = Black

                                      TABLE 2    __________________________________________________________________________    Color response of iodine-polymer complex to increasing peracetic acid    concentration               Peracetic Acid Concentration, ppm    Polymer Type               100  250  500  1000 1500 2000    __________________________________________________________________________    Hydroxypropylcellulose               Yellow                    Y Brown                         Brown                              Brick                                   Dk Coffee                                        Bk Coffee    Hydroxyethylcellulose               Y Brown                    Lt Brown                         Brown                              Dk Coffee                                   Bk Coffee                                        Bk Coffee    Carboxymethylcellulose               Y Brown                    Lt Brown                         Brown                              Dk Coffee                                   Bk Coffee                                        Bk Coffee    Polyvinylpyrrolidone               Y Brown                    Lt Brown                         Brown                              Dk Brown                                   Dk Brown                                        Bk Coffee    (PVP)    Starch     Bk Blue                    Bk Blue                         Bk Blue                              Bk Blue                                   Bk Blue                                        Bk Blue    __________________________________________________________________________

The results set forth in Tables 1 and 2 show that a test strip of thepresent invention is capable of assaying for hydrogen peroxide over theentire range of 0% to greater than 4% by weight, and for peracetic acidover the entire range of 0 to 2000 ppm, by providing a differentiablecolor response over these entire ranges. Accordingly, a single teststrip can be used to assay for a low or a high concentration ofperoxide, without diluting the test sample.

In particular, Tables 1 and 2 show that the color transition attributedto an increasing concentration of peroxide varies for differentpolymers. For example, the hydroxypropylcellulose-iodine complex has aslightly weaker color intensity at higher peroxide concentrationscompared to a hydroxyethylcellulose-iodine complex. It was found thatusing both polymers in an indicator reagent composition in a ratio ofabout 5:1, for example, gave a more intense color transition and a moredifferentiable response to a wide range of peroxide concentrations, andespecially a high peroxide concentration.

The results summarized in Tables 1 and 2 also show that in the highperoxide concentration range (e.g., about 0.1% by weight or greater) thecolor differentiation between different peroxide concentrations isrelatively easy to distinguish. The color transitions in the highperoxide range are particularly useful in ensuring that hemodialysisunits are properly cleaned between patients because the sanitizingsolution needed to clean the hemodialysis unit requires a high peroxideconcentration.

In another test designed to illustrate the ability of a presentindicator reagent composition to quantitatively assay a test sample fora high concentration of peroxide, filter paper was impregnated withpotassium iodide, hydroxypropylcellulose, and a buffer, as describedabove. The impregnated filter paper was used to prepare dry phase teststrips. Individual test strips were used to test aqueous solutionscontaining 0.2% to 4% RENALIN®. RENALIN® is a commercial peroxide-baseddisinfectant solution marketed by Renal Systems, Division of MinntechCorporation, Minneapolis, Minn., and contains about 4% peracetic acidand about 20% hydrogen peroxide. Table 3 summarizes the color responseof the test strips to the different concentrations of RENALIN®. All teststrips were colorless prior to contact with a RENALIN® solution.

                  TABLE 3    ______________________________________    RENALIN ® Concentration                      Color Transition    ______________________________________    0.2%              Yellow    0.5%              Y Brown    1.0%              Lt Brown    2.0%              Brown    3.0%              Brick    3.5%              Dk Brown    4.0%              Bk Brown    ______________________________________

The data summarized in Table 3 show that a dry phase test strip of thepresent invention can be used in a quantitative assay for peroxide in anaqueous test sample. Table 3 also shows that the assay can be performedon a test sample containing a mixture of peroxides. Prior assays forperacetic acid are based on a starch-iodine complex, and could onlydetermine whether peracetic acid was present in an amount of 500 ppm orgreater. These prior tests are unable to provide a quantitative assayfor peroxide either above or below 500 ppm.

An indicator reagent composition of the present invention that includesa water-soluble polymer, in addition to an iodide salt and a buffer tobuffer the composition to a pH of about 2 to about 9, therefore,exhibits a sufficiently dramatic color transition, from light yellow todark brown, to provide a sensitive and accurate assay for peroxide in anundiluted test sample. The color transition also is sufficientlyresolvable and differentiable, either visually or by instrument, suchthat an unknown concentration of peroxide in a test sample can bedetermined.

As previously stated, an important feature of the present invention isto provide a quantitative assay for peroxide in the high detection rangeof 0.1% by weight or greater. This was difficult to achieve using priortest strips unless the test sample was diluted to reduce the peroxideconcentration to within the detectable range of the test strip. Testsample dilution is undesirable because of the time involved and becauseof the distinct possibility of dilution error, and, in turn, assayerror.

An assay having a broad peroxide detection range allows the user todirectly monitor, without dilution, the effective peroxide level of asanitizing or disinfecting solution. In particular, a 3.5% RENALIN®solution, which commonly is used in hemodialysis operations to sanitizethe dialysis system, can be assayed using a present test strip. Theproblem with currently available test strips is that the detectionranges are either narrow and confined to a specific range or are merelyqualitative tests. No present test strip has a detection range to assayfor both low, middle, and high concentration levels of peroxide, withoutdilution of the test sample.

From the visual assays and the data presented in Tables 1-3, it has beendemonstrated that an indicator reagent composition of the presentinvention accurately assays for high levels of peroxide, directly andquantitatively, and without test sample dilution. In preferredembodiments, the composition contains a mixture of water-solublepolymers, each having a different response intensity and response rangeto peroxide levels. If desired, the composition then can be adjusted todetect and measure a specific peroxide range. The color differentiationsbetween different peroxide levels are excellent, therefore, thecomposition can be used in a quantitative test, rather than aqualitative, positive-negative test.

In accordance with an important feature of the present invention, thecontinuing and substantial problems in dry phase test strips forquantitatively assaying an undiluted test sample for a highconcentration of peroxide are essentially eliminated. An indicatorreagent composition of the present invention provides a differentiableresponse to peroxide over the concentration range of 0% to greater thanabout 4%, and particularly about 0.1% to greater than about 4%, byweight of the test sample. Therefore, accurate and reliable assays forperoxide in test samples can be performed by utilizing an indicatorreagent composition and device of the present invention.

Obviously, many modifications and variations of the invention ashereinbefore set forth can be made without departing from the spirit andscope thereof, and, therefore, only such limitations should be imposedas are indicated by the appended claims.

What is claimed is:
 1. A composition capable of exhibiting a detectableand measurable color transition in response to a peroxide concentrationof 0% to greater than 4%, by weight, said composition comprising:(a) aniodide salt; (b) a buffer; (c) a water-soluble polymer comprising acellulose-based polymer; and (d) a carrier comprising water, wherein thecomposition has a pH of about 2 to about
 9. 2. The composition of claim1 wherein the iodide salt is present in an amount of about 1% to 4%, byweight of the composition.
 3. The composition of claim 1 wherein theiodide salt comprises potassium iodide, sodium iodide, lithium iodide,or a mixture thereof.
 4. The composition of claim 1 wherein thewater-soluble polymer is present in an amount of about 0.1% to about 5%,by weight of the composition.
 5. The composition of claim 1 wherein thecellulose-based polymer is selected from the group consisting ofmethylcellulose, hydroxymethylcellulose, hydroxyethylcellulose,hydroxyethylmethylcellulose, hydroxypropylcellulose,hydroxypropylmethylcellulose, carboxymethylcellulose and salts thereof,hydroxybutylcellulose, cellulose acetate,carboxymethylhydroxyethylcellulose, hydroxybutylmethylcellulose, andmixtures thereof.
 6. The composition of claim 1 wherein thewater-soluble polymer comprises a mixture of cellulose-based polymers.7. The composition of claim 1 wherein the water-soluble polymercomprises hydroxypropylcellulose.
 8. The composition of claim 7 whereinthe water-soluble polymer further comprises hydroxyethylcellulose,carboxymethylcellulose, methylcellulose, hydroxymethylcellulose, andmixtures thereof.
 9. The composition of claim 1 wherein the buffer ispresent in an amount of about 1% to about 15%, by weight of thecomposition.
 10. The composition of claim 1 wherein the buffer isselected from the group consisting of a polycarboxylic acid wherein thecarboxyl groups are separated by two to five carbon atoms, citric acid,succinic acid, ketoglutaric acid, lactic acid, phosphate, borate,acetate, and mixtures thereof.
 11. The composition of claim 1 whereinthe composition has a pH of about 4 to about
 7. 12. The composition ofclaim 1 further comprising an anionic or a nonionic surfactant in anamount of 0% to about 1.5% by weight of the composition.
 13. Thecomposition of claim 12 wherein the nonionic surfactant is selected fromthe group consisting of an ethoxylated polysorbate, an ethoxylatedalcohol, an ethoxylated phenol, a polyethylene glycol, a polypropyleneglycol, an ethylene glycol-propylene glycol copolymer, a polybutyleneglycol, and mixtures thereof.
 14. The composition of claim 12 whereinthe anionic surfactant comprises a sulfate, a sulfonate, a carbonate, aphosphate, or a carboxylate.
 15. The composition of claim 12 wherein theanionic surfactant is selected from the group consisting of an alkylsulfate, an alkyl ether sulfate, an alkyl ether sulfonate, a sulfateester of an alkylphenoxy polyoxyethylene ethanol, an alpha-olefinsulfonate, a beta-alkyloxy alkane sulfonate, an alkyl arylsulfonate, analkyl carbonate, an alkyl ether carboxylate, a fatty acid, asulfosuccinate, an alkyl ether sulfosuccinate, a sarcosinate, anoctoxynol phosphate, a nonoxynol phosphate, a taurate, a fatty tauride,a sulfated monoglyceride, a fatty acid amido polyoxyethylene sulfate,and mixtures thereof.
 16. The composition of claim 1 wherein the carriercomprises 0% to about 90% by weight of the carrier of an organicsolvent.
 17. The composition of claim 1 comprising:(a) about 1.5% toabout 3% by weight potassium iodide; (b) about 5% to about 12% by weightof a buffer selected from the group consisting of a polycarboxylic acidhaving carboxyl groups separated by two to five carbon atoms; (c) about0.2% to about 3% by weight of hydroxypropylcellulose,hydroxyethylcellulose, methylcellulose, hydroxymethylcellulose,carboxymethylcellulose, or mixtures thereof; and (d) a carriercomprising water, wherein the composition has a pH of about 5 to about6.5.
 18. The composition of claim 17 comprising about 0.2% to about 2.5%by weight of a mixture of hydroxypropylcellulose, hydroxyethylcellulose,and polyvinylpyrrolidone.
 19. A method of determining peroxide contentof an aqueous test sample containing 0% to greater than 4% by weightperoxide, said method comprising:(a) contacting the aqueous test samplewith an indicator reagent composition comprising:(i) an iodide salt,(ii) a buffer, (iii) a water-soluble polymer comprising acellulose-based polymer, and (iv) a carrier comprising water, (b)determining the peroxide content of the aqueous test sample from theintensity and degree of a color transition of the indicator reagentcomposition.
 20. The method of claim 19 wherein the aqueous test samplehas a peroxide content of 0.1% to greater than 4% by weight peroxide.21. The method of claim 19 wherein the aqueous test sample is anundiluted test sample.
 22. The method of claim 19 wherein the intensityand degree of the color transition are determined visually orinstrumentally.
 23. A method of quantitatively determining the peroxidecontent of an aqueous sample containing 0% to greater than 4% by weightperoxide, said method comprising:(a) contacting the aqueous sample withan analyte detection device comprising a test pad, said test pad havingincorporated therein an indicator reagent composition comprising:(i) aniodide salt, (ii) a buffer, (iii) a water-soluble polymer comprising acellulose-based polymer, and (iv) a carrier comprising water, (b)determining the peroxide content of the aqueous sample from theintensity and degree of a color transition of the indicator reagentcomposition.
 24. The method of claim 23 wherein the peroxide is ahydroperoxide having the formula R--OOH, wherein R is selected from thegroup consisting of alkyl, phenyl-substituted alkyl, and cycloalkyl,wherein the alkyl group has one to ten carbon atoms, a peracid havingthe formula R₁ --CO₃ H, wherein R₁ is selected from the group consistingof hydrogen, phenyl, alkyl, and cycloalkyl, wherein the alkyl group has1 to 15 carbon atoms, or a mixture thereof.
 25. The method of claim 23wherein the peroxide comprises hydrogen peroxide, a peracetic acid,benzoyl peroxide, performic acid, or a mixture thereof.
 26. A method ofdetermining the peroxide content of an aqueous sample comprising:(a)contacting the aqueous sample with an analyte detection devicecomprising a test pad having incorporated therein:(i) an iodide salt,(ii) a buffer, (iii) a water-soluble polymer comprising acellulose-based polymer, and (iv) a carrier comprising water, (b)examining the analyte detection device for a color transition; and (c)correlating the color transition to the peroxide content of the aqueoussample.
 27. The method of claim 26 wherein the aqueous sample has aperoxide content of 0% to about 4% by weight.
 28. The method of claim 26wherein the peroxide is hydrogen peroxide, peracetic acid, benzoylperoxide, performic acid, or a mixture thereof.
 29. An analyte-detectiondevice to determine the peroxide content of an aqueous test samplecomprising:a support strip; a test pad; and an indicator reagentcomposition incorporated into the test pad, said reagent compositioncomprising:(a) an iodide salt, (b) a buffer, (c) a water-soluble polymercomprising a cellulose-based polymer, and (d) a carrier comprisingwater.
 30. A composition capable of exhibiting a detectable andmeasurable color transition in response to a peroxide concentration of0% to greater than 4%, by weight, said composition comprising:(a) aniodide salt; (b) a buffer; (c) a water-soluble polymer comprisingpolyvinylpyrrolidone, hydrolyzed polyvinylpyrrolidone, poly(vinylalcohol), poly(vinyl acetate), a vinyl acetate-vinyl alcohol copolymer,polyvinyloxazolidone, polyvinylmethyloxazolidone, a copolymer ofvinylpyrrolidone and a vinyl amide of γ-amine butyric acid, apolyacrylic acid polymer, a polyacrylic acid copolymer, a partially orfully neutralized salt of a polyacrylic acid polymer or a polyacrylicacid copolymer, poly(methacrylic acid), poly(methacrylamide),poly(N,N-dimethylacryamide), poly(N-isopropylacrylamide),poly(N-acetamidoacrylamide), poly(N-acetamidomethacrylamide), an acrylicinterpolymer of polyacrylic acid with poly-(methacrylic acid),polyacrylic acid with poly(methacrylamide), polyacrylic acid withmethacrylic acid, a polyoxypropylene-polyoxyethylene block polymerhaving a structure: ##STR2## wherein x and z, independently, are aninteger from 4 to 30, and y is an integer from 4 to 100, polyacrylamide,a copolymer of acrylamide, an acrylamide/sodium acrylate copolymer, anacrylate/acrylamide copolymer, an acrylate/ammonium methacrylatecopolymer, an acrylate/diacetoneacrylamide copolymer, anacrylic/acrylate copolymer, an adipic acid/dimethylaminohydroxypropyldiethylenetriamine copolymer, an ammonium acrylate copolymer, anammonium styrene/acrylate copolymer, an ammonium vinyl acetate/acrylatecopolymer, an aminomethylpropanol acrylate/diacetoneacrylamidecopolymer, an aminomethylpropanediol acrylate/diacetoneacrylamidecopolymer, a butyl benzoic acid/phthalic anhydride/trimethylolethanecopolymer, a diethylene glycolamine/epichlorohydrin/piperazinecopolymer, an ethylene/vinyl alcohol copolymer, an ethyl ester ofpolyethylenimine, an isopropyl ester of methyl vinyl ether/maleicanhydride copolymer, a melamine/formaldehyde resin, a methoxyethyleneglycol/dodecyl glycol copolymer, an octadecene/maleic anhydridecopolymer, an octylacrylamide/acrylate/butylaminoethyl methacrylatecopolymer, an octylacrylamide/acrylate copolymer, a polyethyleneglycol/dodecyl glycol copolymer, a polyethyleneimine, phthalicanhydride/glycerin/glycidyl decanoate copolymer, a metal salt ofpolyacrylic acid, a metal salt of a methyl vinyl ether/maleic anhydridecopolymer, a vinylpyrrolidone/eicosene copolymer, avinylpyrrolidone/ethyl methacrylate/methacrylic acid copolymer, avinylpyrrolidone/hexadecene copolymer, a vinylpyrrolidone/vinyl acetatecopolymer, a polyvinylpyrrolidone/vinyl acetate/itaconic acid copolymer,a sodium acrylate/vinyl alcohol copolymer, sodium polymethacrylate,sodium polystyrene sulfonate, a sodium styrene/acrylate/polyethyleneglycol-10 dimaleate copolymer, a sodium styrene/polyethylene glycol-10maleate/nonoxynol-10 maleate/acrylate copolymer, a styrene/acrylamidecopolymer, a styrene/acrylate/ammonium methacrylate copolymer, astyrene/maleic anhydride copolymer, a styrene/polyvinyloxazolidonecopolymer, a urea formaldehyde polymer, a urea/melamine/formaldehydepolymer, a vinyl acetate/crotonic acid copolymer, a vinyl alcoholcopolymer, and mixtures thereof; and (d) a carrier comprising water,wherein the composition has a pH of about 2 to about
 9. 31. Thecomposition of claim 30 wherein the iodide salt is present in an amountof about 1% to 4%, by weight of the composition.
 32. The composition ofclaim 30 wherein the iodide salt comprises potassium iodide, sodiumiodide, lithium iodide, or a mixture thereof.
 33. The composition ofclaim 30 wherein the water-soluble polymer is present in an amount ofabout 0.1% to about 5%, by weight of the composition.
 34. Thecomposition of claim 30 comprising:(a) about 1.5% to about 3% by weightpotassium iodide; (b) about 5% to about 12% by weight of a bufferselected from the group consisting of a polycarboxylic acid havingcarboxyl groups separated by two to five carbon atoms; (c) about 0.2% toabout 3% by weight of polyvinylpyrrolidone; and (d) a carrier comprisingwater, wherein the composition has a pH of about 5 to about 6.5.
 35. Thecomposition of claim 30 wherein the water-soluble polymer furthercomprises a cellulose-based polymer.
 36. The composition of claim 30wherein the water-soluble polymer further comprises a mixture ofcellulose-based polymers.